Top drain LDMOS

ABSTRACT

In an embodiment, this invention discloses a top-drain lateral diffusion metal oxide field effect semiconductor (TD-LDMOS) device supported on a semiconductor substrate. The TD-LDMOS includes a source electrode disposed on a bottom surface of the semiconductor substrate. The TD-LDMOS further includes a source region and a drain region disposed on two opposite sides of a planar gate disposed on a top surface of the semiconductor substrate wherein the source region is encompassed in a body region constituting a drift region as a lateral current channel between the source region and drain region under the planar gate. The TD-LDMOS further includes at least a trench filled with a conductive material and extending vertically from the body region near the top surface downwardly to electrically contact the source electrode disposed on the bottom surface of the semiconductor substrate.

This patent application is a Continuation in Part Application ofapplication Ser. No. 13/095,539 filed on Apr. 27, 2011 now U.S. Pat. No.8,816,476 by a common Inventor of this Application. The Disclosures madein the patent application Ser. No. 13/095,539 are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the semiconductor power devices. Moreparticularly, this invention relates to an inverted grounded sourcelateral diffusion metal oxide semiconductor field effect transistor(LDMOSFET) structure and manufacturing method.

2. Description of the Prior Art

Conventional technologies to further reduce the source inductance forsemiconductor power devices including the source inductance in FET,MOSFET and JFET devices are challenged by several technical difficultiesand limitations. Specifically, there are technical challenges faced bythose of ordinary skill in the art to reduce the source inductance.Meanwhile, there are ever increasing demand to reduce the sourceinductance in the semiconductor power devices because more and morepower devices are required for applications that demand these devices tofunction with high efficiency, high gain, and high frequency. Generally,reduction of source inductance can be achieved by eliminating thebond-wires in the package of a semiconductor power device. Many attemptsare made to eliminate the bond-wires by configuring the semiconductorsubstrate as a source electrode for connection of the semiconductorpower devices. There are difficulties in such approaches due to thefacts that typical vertical semiconductor power devices is arranged toplace the drain electrode on the substrate. The vertical power devices,either as trenched gate or planar gate DMOS devices, use the substrateas the drain electrode with the current flowing vertically from thesource region disposed at the top of the substrate down to the drainregion disposed at the bottom of the substrate and the top sourceelectrode usually requires bond wires for electrical connections duringa device packaging process thus increasing the source inductance.

Several lateral DMOS with bottom source have been disclosed as priorart. A lateral DMOS device typically includes a deep P+ sinker region(an implant sinker or a trench sinker) within the source contact toconnect the top source to the P+ substrate resulting in a large cellpitch due to the dimensions occupied by the sinker region, or on theoutside of the cell resulting in higher source resistance. G. Cao et al.in “Comparative Study of Drift Region Designs in RF LDMOSFETs”, IEEEElectron Devices, August 2004, pp 1296-1303, disclose a bottom sourcelateral LDMOS device, as shown in FIG. 1A, includes a deep sinkerdiffused within the source contact.

Ishiwaka O et al. disclose in “A 2.45 GHz power Ld-MOFSET with reducedsource inductance by V-groove connections”, International ElectronDevices Meeting—Technical Digest, Washington, D.C., USA, 1-4 Dec. 1985,pp. 166-169, discloses a lateral double-diffused MOS field effecttransistor (LD-MOSFET) with V-grooved source connections employed tominimize the source inductance, the gate-to-drain capacitance and thechannel length. The V-grooves, which penetrate the P⁻ type epitaxiallayer and reach the P⁺ type substrate, are formed in the SiO2 regionjust outside the active area. The N⁺ type source regions of theLD-MOSFET are directly connected to the V-grooves with metallization,thus eliminate the bonding wires for the source.

In U.S. Pat. No. 6,372,557 (Leong, Apr. 16, 2002), which discloses abottom source lateral LDMOS device, attempts are made to use a buriedlayer at the interface of the P+ and P-epitaxial layers to reduce thelateral diffusion and hence reduce cell pitch. U.S. Pat. No. 5,821,144(D'Anna et al., Oct. 13, 1998) and U.S. Pat. No. 5,869,875 (Hébert, Feb.9, 1999) also disclose lateral DMOS devices that include a deep sinkerregion (an implant sinker or a trench sinker) on the OUTER periphery ofthe structure to reduce the cell pitch.

However, in these disclosures, the devices use a single metal over thesource/body contact regions and gate shield regions, which is thick (3um or more) then due to its thickness it will have higher capacitancefrom the source metal to N-drift drain, more stress on the gate and alsolarger spacing to drain metal, thus increases the cell pitch. In theother hand, some of the devices use a first metal for the source/bodycontact regions and a second metal for drain and gate shield regions,then the first metal is thinner so it can wrap around the gate andshield it with lower capacitance and less stress and does not affect thecell pitch. However, using two metals adds cost since it needs two extramasks—one for via and the other for top metal. These configurationsgenerally form the P+ sinker through top down diffusion resulting inlarge cell pitch due to the significant lateral diffusions of the deepsinker used to connect the top source down to the highly dopedsubstrate, which increases the overall size of the cell over thehorizontal plane. A large cell pitch causes a large on-resistance thatis a function of resistance and device areas. A large cell pitch alsoincreases the device costs due to a larger size of the device and alarger size package. Furthermore, reducing the cell pitch of these priorart bottom-source devices results in shifts in the electricalperformance of the device. For example, bringing the diffused sinker(which is p+ in doping) closer to the source side of the gate in FIG. 1Awill result in a higher threshold voltage since the lateral diffusion ofthe diffused p+ sinker used to connect the top source to the bottomsubstrate will encroach in the channel region under the gate, which isalso p-type, increase the doping concentration in the channel and hence,increase the threshold voltage, which is an undesirable result.

U.S. Pat. No. 7,554,154 discloses an improved inverted ground-source FETon highly doped substrate, e.g., highly doped P+ substrate, as shown inFIG. 1B, with a self-aligned body-source contact for a reduced cellpitch. The improved FET includes an integrated body-source shortstructure, i.e., the P+ sinker, which diffuses at the lower portionunder the channel and toward the drain. The P+ sinker extends undersurface channel to compensate drain extension doping, thus lower Cgd andreduce the cell pitch. In addition, the dopant concentration of theaccumulation region is fine tuned to minimize Cgd*Rdson figure of merit.With this top drain LDMOS structure, a buried gate shield is implementedfor body-source contact and to reduce the gate to drain capacitance Cgdand the device cells are arranged in a closed configuration that canfurther reduce extra space required for termination. However,significant lateral diffusions of the deep P+ sinker used to connect thetop source down to the highly doped substrate occupies greater spacethus limiting further reduction and shrinking of the cell pitches.

Therefore, a need still exists in the art of power semiconductor devicedesign and manufacture to provide new device configurations andmanufacturing method in forming the power devices such that the abovediscussed problems and limitations can be resolved.

SUMMARY OF THE PRESENT INVENTION

It is therefore an aspect of the present invention to provide a new andimproved top-drain lateral diffusion MOS (TD-LDMOS) semiconductor powerdevice implemented with a trench source-body interconnect extending fromthe top surface through the body region down to the bottom sourceelectrode. The device configuration has a reduced cell pitch forreducing die costs such that the above discussed technical difficultiesand limitations can be overcome.

Specifically, it is an aspect of the present invention to provide animproved top-drain lateral diffusion MOS (TD-LDMOS) semiconductor powerdevice implemented with a trench source-body interconnect that has abottom substrate source connection such that the source inductance canbe significantly reduced to achieve high efficiency, high gain and highfrequency applications by the power device.

It is another aspect of the present invention to provide an improvedtop-drain lateral diffusion MOS (TD-LDMOS) semiconductor power deviceimplemented with a trench source-body interconnect extending from thetop surface through the body region down to the bottom source electrodewith a narrow opening and high aspect ratio such that the cell pitch canbe significantly reduced and the mask requirement can be reduced tofurther reduce the fabrication costs for production of high quality andreliable semiconductor power devices.

It is another aspect of the present invention to provide an improvedtop-drain lateral diffusion MOS (TD-LDMOS) semiconductor power deviceimplemented with a trench source-body interconnect extending from thetop surface through the body region down to the bottom source electrodewith the trench filled with SEG P++ or SEG P++ SiGe or metal fillingmaterial. The trench is further surrounded with P++ liner implantregions below the trench bottom surface and around the trench sidewallsto further reduce the interconnect resistance between the body andsource disposed at the bottom surface.

It is another aspect of the present invention to provide an improvedtop-drain lateral diffusion MOS (TD-LDMOS) semiconductor power deviceimplemented with a trench source-body interconnect extending from thetop surface through the body region down to the bottom source electrodewherein a gate shield Ti/TiN layer and a salicide layer are formedcovering an insulation layer above the gate insulation layer and a topsurface of a body region such that the gate-to-drain capacitance can befurther reduced. Therefore, the device disclosed in this invention isrugged and highly reliable such that the device configuration is muchmore scalable to compatibly operable with high and low voltageapplications.

Briefly in a preferred embodiment this invention discloses a top-drainlateral diffusion metal oxide field effect semiconductor (TD-LDMOS)device supported on a semiconductor substrate. The TD-LDMOS includes asource electrode disposed on a bottom surface of the semiconductorsubstrate. The TD-LDMOS further includes a source and a drain regiondisposed on two opposite sides of a planar gate disposed on a topsurface of the semiconductor substrate wherein the source region isencompassed in a body region constituting a drift region as a lateralcurrent channel between the source region and drain region under theplanar gate. The TD-LDMOS further includes at least a trench filled witha conductive material and extending vertically from the body region nearthe top surface downwardly to electrically contact the source electrodedisposed on the bottom surface of the semiconductor substrate.

Furthermore, this invention discloses a method for manufacturing asemiconductor power device on a semiconductor substrate. The methodincludes a step of 1) forming a body region encompassing a source regionand a drain region with a gate on a top surface of the semiconductorsubstrate for controlling a lateral current path in the body regionbetween the source region and a drain region near the top surface of thesubstrate; and 2) opening a trench extending from the body regiondownwardly to a source electrode on a bottom surface of the substrateand filling the trench with a conductive material to function as abody-source interconnect. In an embodiment, the step of filling thetrench with a conductive material comprises a step of filling the trenchwith the conductive material comprising a selective epitaxial growth(SEG) of silicon or a SEG of silicon-germanium (SiGe). In anotherembodiment the method further includes a step of implanting a heavilydoped liner region below the bottom of the trench and surroundingsidewalls of the trench

These and other objects and advantages of the present invention will nodoubt become obvious to those of ordinary skill in the art after havingread the following detailed description of the preferred embodiment,which is illustrated in the various drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross sectional view of a conventional lateral diffusionMOS (LDMOS) device with a bottom source used for RF base stationamplifier.

FIG. 1B is a cross sectional view of bottom source LDMOS with diffusedsinker region disclosed in a referenced patent.

FIG. 2A is a cross sectional view of a top drain LDMOS device withtrench body-source short structure as an embodiment of this invention.

FIG. 2B is a cross sectional view illustrating a whole TD-LDMOS devicecell that can be arranged in a closed cell configuration.

FIG. 2C is a top view illustrating a whole TD-LDMOS device cell that canbe arranged in a closed cell configuration.

FIG. 3 is a cross sectional view of another top drain LDMOS device asanother embodiment of this invention.

FIGS. 4A to 4L are a serial cross sectional views for describing themanufacturing processes to fabricate a TD-LDMOS device of thisinvention.

DETAILED DESCRIPTION OF THE METHOD

Referring to FIG. 2A for a cross sectional view of an N-channel invertedtop drain and ground-source trenched FET device with a top drain and abottom source of this invention. The inverted top-drain ground-sourceN-channel FET device is supported on a P+ substrate 105 functioning as abottom source electrode. Alternatively, a P-channel device may be formedover an N+ Si substrate. A layer of P− epitaxial layer 110 is supportedon top of the substrate 105. The substrate is configured with an activecell area and a termination area typically disposed on the peripheral ofthe substrate. A deep trench 120 with a high aspect ratio is openedthrough the epitaxial layer 110 and extending downwardly to thesubstrate 105. Selective epitaxial growth (SEG) of silicon or SEG ofsilicon-germanium (SiGe) with a heavily P doped P++ is performed to fillthe deep trench 120 forming a self-aligned source/body contactfunctioning as an ultra-low resistive local interconnect from source tobody and to the substrate. For the purpose of improving the contact, aP++ liner implant region 128 is formed with angled P++ implant below thebottom of the trench and surrounding the sidewalls of the source-bodyinterconnect trench 120 before the P++ conductive trench fillingmaterial is filled in the trench. A body region 115 is formed in theupper portion of the epitaxial layer 110 that extends laterally to adrain drift region 125. The P−dopants in the body region 115 compensatesome of the N−dopant in the accumulation of the transistor for tailoringa dopant profile of N-drift region 125 to minimize the gate-draincapacitance while maintaining a low drain to source resistance Rdson . .. . The deep trenched source-body interconnect 120 further extendsvertically both downward to the bottom P+ substrate 105, and upward tothe body region 115. Part of the body region 115 forms a channel at atop surface under a gate oxide 135. The deep trenched source-bodyinterconnect 120 has a narrow opening and high aspect ratio such thatthe cell pitch can be reduced without requiring a sinker region that isformed with a lateral diffusion expansion for the purpose of extendingthe sinker region to a greater depth to reach the bottom source region105.

A stacked planar gate 140 surrounded by a gate spacer 165 and covered bya gate shield metal 170-G is disposed above the gate oxide layer 135formed on the top surface between the source region 160 and the draindrift region 125. The gate 140 thus controls the current flow betweenthe source region 160 and the drain drift region 125 through the channelform by body region 115 under the gate 140 to function as a lateral MOSdevice. The drain drift region 125 is disposed below a field oxide 130covered by a BPSG layer 180 and optionally a passivation layer 185. Adrain contact opening is etched through the passivation layer 185 andthe BPSG layer 180 for the top drain metal 199 to contact the drainregion 125 via a contact N+ dopant region 190 with reduce contactresistance. The stacked gate 140 with the oxide 130 and 135 below thestacked gate 140 as shown may be formed by different methods. Themethods include the processes of growing or depositing the oxide andetching from the channel region or by using a LOCOS type of oxidationprocess. The stacked gate 140 has a longer gate length and field platingover the drain extension without increasing the cell pitch. The stackedgate 140 controls the link for current to flow between the channel andthe drain under the gate oxide 135 and field oxide 130 with reducedgate-drain capacitance. The stacked gate 140 is surrounded by insulationspacer 165 and surrounded by a buried gate shield 170-G that furtherincludes a salicide portion 170-S for body-source contact and to furtherreduce the gate to drain capacitance Cgd with the gate shield layer170-G shields the drain metal 199 covering over the top surface. Forbetter mechanical and electrical performance, a barrier Ti/TiN linerlayer 198 is further formed between the drain contact region 190 and thedrain metal 199. The half pitch of the cell is significantly reducedwith the self-aligned source-body interconnected formed as trenchinterconnect 120 filled with the selective epitaxial growth (SEG) P++ Sior SEG P++ SiGe such that no sinker diffusion is required.

FIG. 2B is a cross-sectional view illustrating a whole cell of theTD-LDMOS device of this invention, which can be arranged in a closedcell configuration. As shown in FIG. 2B, both sources of the half cellpitch are grounded, thus space savings are achieved because there is noneed to provide the extra space for termination area for this TD-LDMOSdevice. FIG. 2C is a top view of a whole cell of the TD-LDMOS device ofthis invention, which can be arranged in a closed cell configuration.

FIG. 3 is another exemplary embodiment of the TDLDMOS device that issimilar to the device shown in FIG. 2. The only difference is that thedevice is formed on a heavily doped N++ substrate 101 to substantiallyreduce the series resistance. The P+ epitaxial layer 105 functioning asa bottom source electrode is formed on top of the N++ substrate 101 andshorted to the N++ substrate, thus reduce the resistance of thesubstrate. Furthermore, as an optional, a deep buffer layer 115 isformed within the P− epitaxial layer 110 at a predetermined depth andabove the P+ source layer 105 for the purpose of breakdown voltage (BV)adjustment and sub-surface punch-through prevention due to thermalcycles as that required in the manufacturing processes. In thisembodiment, the deep trench 120 opens through the P-epitaxial layer 110and the P+ source layer 105 extends downwardly to the N++ substrate 101.As that described above in FIG. 2A, the deep trench 120 has a highaspect ratio and is filled with a heavily P doped P++ conductivematerial such as selective epitaxial growth (SEG) of silicon or SEG ofsilicon-germanium (SiGe). Alternatively, the deep trench 120 can befilled with P++ poly or with a metal, such as tungsten, with a metalliner 129, for example salicide Ti/TiN, forming an ultra-low resistivelocal interconnect between the drain and the source. The passivationlayer 185 can be omitted with this device configuration.

FIGS. 4A to 4L are a series of cross sectional views to illustrate themanufacturing processes for making a device structure as shown in FIGS.2A and 3. As will be understood from the disclosures made in through thedescriptions of the manufacturing steps, the processes only require sixmasking steps because of a beneficial Self-Aligned Structure. As shownin FIG. 4A, the processes start with a starting silicon substrate thatincludes a P+ substrate 205 doped with Boron with a resistivity of 3 to5 mOhm-cm or a lower resistivity. The substrate 205 is preferably alonga <100> crystal orientation as a standard prime. A P− epitaxial layer210 is formed on the substrate 205 with a thickness ranging from 2 to 7micrometers and typically doped with a low dosage of 5E14 to 5E15 for20-60 volts application. In another embodiment, the epitaxial layer 210may be an N− doped layer.

In FIG. 4B, a pad oxide layer 212 is grown for a nitride deposition steplater in process. As an optional processing step, a blanket deep bufferlayer implant with an implant dose of 1E14 at an implant energy ofapproximately 600 KEV is performed to form a deep buffer layer 215 forthe purpose of breakdown voltage (BV) adjustment and sub-surfacepunch-through prevention between the N-drift layer, formed in laterprocess, and P+ substrate 205 due to thermal cycles as that requiredlater on when subsequent manufacturing processes are carried out. It canbe a lightly doped blanket P implant to increase the P− doping to avoidpunch through or it can be a lightly doped N-implant for an N-epitaxiallayer.

A nitride deposition is carried out on top of the pad oxide layer 212and then etched using an active mask, first mask, which is not shown, toprotect the channel region and expose the drain extension region duringthe subsequent processing. An N-drift implant is performed in theregions not protected by nitride at a zero degree tilt to form theN-drift region 225 as shown in FIG. 4C. The N-drift region 225 can beformed by implanting Phosphorous with an implanting energy rangingbetween 60 Key to 200 Key and a dosage ranging from 5E11 to 2E13 andpreferably a dosage of 3E12 for 30V application. This step results in aself-aligned n-type drift implant (for NMOS) in the drift drainextension of the LDMOS device, region 225. This is followed by astandard field oxidation process (referred to as LOCOS), with optionalN2 drive step, to form field oxide region 230 atop of the N-drift region225. Temperature can be in the range of 900 to 1100 C to grow an oxidewith a thickness in the 0.3 to 1 micron range, with a preferredthickness of about 0.55 microns.

Nitride (not shown) and the pad oxide 212 are stripped followed by asacrificial oxide layer growth and strip (not shown) to clean thesurface of the structure. In FIG. 4D, a gate oxide layer 235 is grownfollowed by depositing a polysilicon layer or preferably a polycidelayer 240 haying a thickness up to 2000 to 6000 Angstroms for forming agate. Then the N+ dopant ions are implanted to the Polysilicon layer andan optional WSix layer is formed on top for providing a low gateresistance contact layer. Note the poly can be in situ doped or dopedusing POCl₃ as well. An oxide cap deposition by using a HTO or LTOprocess is carried out to deposit an oxide cap layer 245 on top of thepolysilicon layer 240. The oxide cap layer 245 has a thickness of about500 to 4500 Angstroms on top of the polysilicon layer 240. A gate mask,i.e., a second mask (not shown), is applied to etch and pattern theoxide cap layer 245 and the gate layer 240. An oxide etch is firstperformed to pattern the oxide cap layer 245 followed by a polysiliconor polycide etch. The polysilicon or polycide etch is stopped on top ofthe gate oxide layer 235 and the field oxide 230 as shown.

In FIG. 4E, a blanket shallow body high angle implantation of boron(high angle implantation to introduce channel under the gate) with adosage range between 1E12 to 1E14, preferably at a dose of 1E13, iscarried out to form the P-body region 250. Optionally, the blanketshallow body implantation at zero angle and higher energy body implantis also carried out to form P-body region 250. With the field oxide 230,the gate 240 and oxide cap 245 stack-structures, the boron ions areimplanted only in the source side of the gate. Then a body drive isperformed with an elevated temperature ranging between 950 to 1150degrees Celsius and preferably at 1050 degree Celsius for approximately60 minutes. In FIG. 4F, a blanket shallow source-implant, for example Asdopant ions implanted with a dosage ranging between 1E15 to 1E16,preferably at 4E15, is carried out to form N+ source region 260. Then asource annealing operation at an elevated temperature ranging between850 C to 1000 C and preferably 950 C is performed for 30 minutes. Someoxygen may be used during the source anneal annealing process dependingon the gate stack to form poly oxide side wall on the edges of thestacked gate 240.

In FIG. 4G, a spacer oxide layer 265 is deposited, which is preferably aconformal oxide layer having a thickness ranging between 1000 to 4000Angstroms and preferably more than 3000 Angstroms to function as a hardmask for body trench etch and isolation for selective epitaxial growth(SEG) and also to passivate gate sidewall in subsequent manufacturingprocesses. Then a source-body local interconnect trench mask, i.e.,third mask, (not shown), is applied then an oxide etch followed by asilicon etch is performed to open a trench 255 with a narrow opening andhigh aspect ratio with a trench depth extends downwardly to reach the P+substrate 205. Then the photoresist (not shown) is removed. A blanketP++ implant at a seven degree tilt implant angle is optionally carriedto implant heavily doped P++ into the trench bottom, also to thesidewall of the trench (not shown), to form the liner implant region 258for better contact. In FIG. 4H, a selective epitaxial growth (SEG) of Sior SiGe with highly doped P++ is performed, preferably a SEG of SiGedoped with P++ boron, to form an ultra-low resistive local interconnect220 from source 260 to body layer 250 and deep buffer layer 215 and tothe substrate 205. In FIG. 4I, an oxide spacer etch is carried out byperforming a reactive ion etch (RIE) to form the gate spacer 265 topassivate gate sidewalls with minimal over etch to assure that there isoxide, 230 and 245, left below the polysilicon gate 240 and on the drainextension.

In FIG. 4J, a slight wet oxide etch is performed to remove the oxide ontop of the N+ source regions 260. Ti or Co is then deposited on topsurface of the silicon to form Ti or Co layer 275′. Then, a firstsalicide formation process is carried out by applying a first rapidthermal annealing (RTA) process to form TiSi or CoSi layer 275′ on thetop surface of the silicon and Ti/TiN layer 275 on top of the oxidelayers 265, 245 and 230. The process is continued by applying a gateshield mask, i.e., fourth mask (not shown), followed with a Ti/TiN wetetch to form the gate shield 275. This mask is not required if the gateshield is not needed. Then the photoresist is removed followed bycarrying out a second salicide formation also carried out with RTA toform TiSi2 or CoSi2 layer 275′ on the top surface of the silicon. Thesilicidation processes form a self-aligned body-source interconnect withgood contact and low resistance and a good gate shield metal with goodinsulation.

In FIG. 4K, an ILD0 material including oxide, nitride or oxy-nitride isdeposited to form the insulation layer 280 followed by applying a drainand gate mask (not shown), i.e., fifth mask, to open the gate contactopening (not shown) and drain contact openings 285 over the insulationlayer 280. A low energy contact implant with phosphorus ions with animplant dosage between 5E14 to 1E 16 is performed to form the lowresistance contact regions 290 followed by an annealing processpreferably using RTA with temperature between 700-900 C in N2 and for atime of 20 sec to 5 minutes, preferably 1 minute. In FIG. 4L, a thickmetal deposition with Ti/TiN liner is carried out to form the drainmetal 295 with barrier metal layer 298. Then a metal mask, i.e., sixthmask (not shown), is applied to perform a metal etch to form the gatemetal and the drain metal on the top surface followed by removing thephotoresist, cleaning up and an alloy process to complete themanufacturing processes.

In another embodiment, which is not shown, the process start with aheavy doped N++ silicon substrate, then a P+ source epitaxial layer isformed on the N++ substrate followed by a growth of a P− epitaxial layeron the P+ source epitaxial layer. The following steps are similar to theprocess steps described above in FIGS. 4B-4K except that the trench 255extends downwardly through the P-epitaxial layer and the P+ sourceepitaxial layer to reach the N++ substrate.

According to above device configuration, a low manufacturing cost isachieved because a lower effective die cost can be achieved by using asmall die by reducing the cell pitch with the trenched source bodyinterconnect without lateral diffusion of the sinker connect region.This reduced cost is able to offset the higher manufacturing costs. Mostimportantly, a low source inductance is achieved through the use of asubstrate source contact while minimizing the source resistance byimplementing the source-body interconnect structure surrounded with P++liner implant regions. Furthermore, a small pitch of the device asdescribed above further reduces the specific-on-resistance (Rsp) for agiven operating voltage. The device configuration is convenientlyscalable for compatible designs and operations adaptable to devices thatrequire a range of high and low voltages.

Therefore, the top drain LDMOS device with an inverted ground-source asdisclosed allows for vertical current through vertical channel withcontrollable drift length of the drift region implemented with thevertical channel enable the manufactures of small and scalable cellpitch. With the source contact at the bottom of the trench in directcontact with the highly doped substrate reduces the source resistance.There is no longer a need for deep resistive sinker region or trenchcontact as that usually implemented in the conventional bottom sourceFET devices.

Although the present invention has been described in terms of thepresently preferred embodiment, it is to be understood that suchdisclosure is not to be interpreted as limiting. Various alterations andmodifications will no doubt become apparent to those skilled in the artafter reading the above disclosure. Accordingly, it is intended that theappended claims be interpreted as covering all alterations andmodifications as fall within the true spirit and scope of the invention.

We claim:
 1. A top-drain lateral diffusion metal oxide field effectsemiconductor (TD-LDMOS) device supported on a semiconductor substratecomprising_(:) a source electrode disposed on a bottom surface of thesemiconductor substrate; a source region and a drain region disposed ontwo opposite sides of a planar gate disposed on a top surface of thesemiconductor substrate with gate sidewalls covered by a gate insulationspacer laterally extending away from the planar gate wherein the sourceregion is encompassed in a body region contacting a drift region as alateral current channel between the source region and drain region underthe planar gate; at least a body-source interconnect trench opened intothe semiconductor substrate vertically aligned with an edge of the gateinsulation spacer wherein the trench is filled with a conductivematerial having a top surface below the top surface of the semiconductorsubstrate for exposing a sidewall of the source region underneath thegate insulation spacer and extending vertically from the body regionnear the top surface of the semiconductor substrate downwardly toelectrically contact the source electrode disposed on the bottom surfaceof the semiconductor substrate; and a gate shield metal layer coveringover the gate insulation spacer and extending laterally over thesidewall surface of the source region underneath the gate insulationspacer and covering a top surface of the body-source interconnecttrench.
 2. The TD-LDMOS device of claim 1 wherein: the semiconductorsubstrate comprising a P+ substrate supporting a P epitaxial layer forforming the source and drain regions of an N type conductivity near thetop surface of the semiconductor substrate.
 3. The TD-LDMOS device ofclaim 2 wherein: the body-source interconnect trench is filled with theconductive material comprising a heavily doped P++ selective epitaxialgrowth (SEG) of silicon or a SEG of silicon-germanium (SiGe).
 4. TheTD-LDMOS device of claim 2 further comprising: a P++ liner implantregion disposed below the bottom of a bottom surface and surrounding thesidewalls of the body-source interconnect trench.
 5. The TD-LDMOS deviceof claim 1 wherein: the planar gate further comprises a stacked planargate padded underneath by a gate oxide layer and covered by a gate capoxide and further having the gate sidewalls surrounded by the gateinsulation spacer.
 6. The TD-LDMOS device of claim 5 further comprising:the gate shield metal layer further covering over the gate cap oxide andthe gate insulation spacer and laterally extends to the sidewall of thesource region underneath the gate insulation spacer and furtherlaterally extends to the top surface of the top surface of thebody-source interconnect trench.
 7. The TD-LDMOS device of claim 1wherein: the body-source interconnect trench is filled with theconductive material comprising a selective epitaxial growth (SEG) ofsilicon or a SEG of silicon-germanium (SiGe).
 8. The TD-LDMOS device ofclaim 1 further comprising: a heavily doped liner implant regiondisposed below a bottom surface of the body-source interconnect trenchand surrounding sidewalls of the body-source interconnect trench.
 9. TheTD-LDMOS device of claim 1 wherein: the body-source interconnect trenchhas a depth to width ratio ranging from 10 to
 25. 10. The TD-LDMOSdevice of claim 1 wherein: the TD-LDMOS device is laterally configuredto have a closed cell layout along a horizontal direction.
 11. TheTD-LDMOS device of claim 1 wherein: the semiconductor substrate furthercomprising a heavily doped bottom layer having an opposite conductivitytype from the body region.
 12. The TD-LDMOS device of claim 1 wherein:the semiconductor substrate further comprising a lateral drift regionimplanted with dopant with a same conductivity type as a conductivitytype of the source region disposed along a lateral direction next to andextends away from the body region for connecting to a top drainelectrode.
 13. The TD-LDMOS device of claim 1 wherein: the TD-LDMOScomprises a P-channel device formed in the semiconductor substratecomprising an N+ Si substrate.
 14. A semiconductor power devicecomprising: a gate disposed on a top surface of a semiconductorsubstrate for controlling a current path between a source region and adrain region disposed near the top surface of the substrate; abody-source interconnect trench filled with a conductive materialcomprising a heavily doped P++ selective epitaxial growth (SEG) ofsilicon-germanium (SiGe) and extends downwardly for shorting the sourceregion to a source electrode disposed on a bottom surface of thesubstrate; and wherein the heavily doped P++ selective epitaxial growth(SEG) of silicon-germanium (SiGe) having a top surface below the topsurface of the semiconductor substrate for exposing a sidewall of thesource region underneath the gate insulation spacer; and a gate shieldmetal layer covering over a gate insulation spacer and extendinglaterally over a sidewall surface of the source region underneath thegate insulation spacer and covering over a top surface of thebody-source interconnect trench.